2002 LS430
121k miles

Hi guys, I've been dealing with an issue I believe was caused be the wrong fluid being put in by the dealer, before I bought the car.

Early on the car would intermittently have surging cruise control. I'd cruise on the freeway and every ten to fifteen seconds it would try to accelerate for only about a second.

Then it started randomly holding the second to third gear shift before finally shifting.

One day it wouldn't shift at all from second to third and would buck and jerk violently when I tried to shift.

I limped the car home, I was able to get it to cruise in fifth, for some reason cruising at a constant speed made the problem disappear. That night I discovered the transmission had some kind of dexron in it, and was overfilled 1.5 quarts. Being midnight all I could do was drain the excess fluid.

The problems went away for a few days and I was finally able to do a drain and fill with 3 quarts of toyota type iv. That helped my issues, they did show up a week later, only this time it would very consistently have trouble shifting from second to third, and would slip.

I also ran into a serious problem, where It would slip in every gear and wouldn't shift at all.

Soon after that, I dropped the transmission pan, changed the filter, cleaned the magnets and the pan, and replaced 6 quarts of fluid.

My problems went away completely for a full week, today I was cruising on the freeway and the transmission dropped from 5th to 4th in cruise control. Dropping it from d5 to d4, then back to d5 got it to shift back into fifth. And going into the city, it was again holding the second to third gear shift, but a couple minutes later the problem went away.

I've been fighting this issue ever since buying the car, and it's the only thing giving me any remorse. Has anyone run into an issue like this or has any suggestions? I've priced out a used transmission, they're easy find since they were put in absolutely everything, I've never changed a transmission in an ls430 before, so not sure if the transmission can be pulled out from the bottom, or if the engine has to come out with it.

Thanks guys.

 

Dexron III and Toyota type IV are actually compatible. Don't know if that is what you suspect. The base is the same but the additives are different. Dexron won't ruin your transmission. I would look that it may not be the transmission clutches. Might be failing shift solenoid(s) or control / electrical. I would at least have Lexus see if they can pull any information before you replace it. Not normal for a 430 transmission to have these issues with the mileage you have.

 

Any error codes?

 

I've been driving around all day with no issues. The problems seem to only come around when cruise control is turned on. I've left it off all day and habrnt encountered any problems. The transmission also acts up when I turn on power mode. I'm gonna drive around all week with out using either to see what happens.

Not pulling any codes from the obd port. Not too sure if theres a special scan tool for the transmission. The lexus dealer did get me some pages from the service manual, and the issues symptoms all fall under a bad ecm. I'll pull out the ecm later this week and look for leaky capacitors. My problems are definitely still intermittent, Im leaning towards an electronic issue based on my observations.

 

On my LS400, not my LS430, I had a similar problem. Short story, the dealer used Dextron rather than T-IV. If you look at the Valvoline spec sheet, it says Dextron is acceptable for T-IV but not recommended. After the Dextron was put in, the transmission shifted very poorly. It missed, shifted unpredictably and generally shifted poorly.

I brought it to the attention of the senior tech, he reluctantly agreed and performed a fluid exchange using T-IV. Problem solved, transmission performance returned to smoothness and predictability. Remember, it was my LS400 and not my LS430.

 

Alright guys, so the issues I've been having with the transmission actually have been pointing towards an electronic issue. The transmission ecm, or shift solenoids in particular. I found a diagram showing where the ecm was, but couldn't find much more info and it's particular location. I figured it was under the center console, but didn't have any luck, after I pulled the trim, and armrest out.

Does anyone have the factory service manual? It would be nice to know a removal procedure or at least confirm the location of the transmission ecm.

 

bump still looking for info.

 

Had a breakthrough two days ago. The transmission acted up and gave me a CEL for P0500 vehicle speed sensor, no signal. I pulled both the speed sensors out and cleaned them, reinstalled them and so far so good. My fuel milage has gone back up, and the erratic shifting has gone away. We'll see if it stays this way.

 

Great to hear! Do you have a diagram to where the speed sensors are?

 

I don't have a diagram. They're very easy to access, I'll take some pictures next time I'm down there.

Sensor A is directly above the dip stick tube on the side of the transmission. It's a very small space to work in, but not the end of the world.

Sensor B is on the drivers side of the transmission near the output shaft. This one is a lot easier do work with. Remove the 10mm bolt, and rotate counter clockwise 90 degrees so the plug faces down. Doing this will allow you to remove it, otherwise it won't clear the transmission tunnel.

To clean them, you can use a clean towel to wipe off any shavings or gunk. It's also safe to use carb cleaner.

You'll want to put atf on the o-rings as well, before installation.

Only one sensor can be bad at a time. If both sensors are bad your transmission will not shift.

Both sensors have the same part number.

 

Thanks! I'm going to clean mine soon.

 

Just wanted to report back. Cleaning the speed sensors indeed was a successful repair. I've driven 500 miles. 200 of them in one trip with no hiccups. The car performed beautifully shifting, power mode, and cruise control all worked properly.

 

Good job! I love the "free" fixes.
I am going to recommend that this be put in for a sticky.

 

Interesting....would love to see exactly where these are located (pictures would be sweet here)....Maybe I should clean mine as well.... If your getting smoother shifting and better MPG, it might be worth me taking a gander over these on my car...

Maybe a maintenance thing ?

 

After work today, I'll climb down there and shoot some pics just for you guys. I have to do a final check for leaks anyways lol.